Specifically, if the global per-user profiles path do not exist and we
cannot create it during the activation, then place our profile in the
Home Manager data directory. We prefer to use the global location,
though, since it makes it visible to `nix-collect-garbage`.
This is intended to improve compatibility with Nix version 2.14 and
later, which no longer creates the per-user directories.
Also, use the Home Manager data directory to manage the gcroot for the
current generation. It does not have to sit in the global per-user
gcroots directory since it should never be eligible for GC.
This adds an empty `nix-build` command to verify that the user is
having a good Nix install. It also, as a side effect, will create the
necessary per-user `profiles` and `gcroots` directories.
Fixes#1246
Using the `nix-env` command is far more robust. It also has the
benefit that if the per-user `profiles` and `gcroots` directories do
not exist then they will be created with the correct permissions.
Because of the second point this commit also removes the `mkdir` step
of the installation instructions.
PR #1239Closes#474, #948, #1091
It is safest to use the system install of Nix since that will be
compatible with the running nix-daemon and/or databases.
Also add a printout of the used Nix version in the activation script
when running in verbose mode.
Fixes#218.
